题解 | 链表内指定区间反转

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 *	ListNode(int x) : val(x), next(nullptr) {}
 * };
 */
class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param head ListNode类 
     * @param m int整型 
     * @param n int整型 
     * @return ListNode类
     */
    ListNode* reverseBetween(ListNode* head, int m, int n) {
        ListNode* dummyHead = new ListNode(0);
        dummyHead->next = head;
        ListNode* pre = dummyHead;
        for (int i = 1; i < m && pre; ++i) pre = pre->next;
        ListNode* tail = pre->next;
        ListNode* cur = tail->next;
        for (int i = 0; i < n - m && cur; ++i) {
            ListNode* tmp = cur->next;
            cur->next = pre->next;
            pre->next = cur;
            tail->next = tmp;
            cur = tmp;
        }
        return dummyHead->next;
    }
};